Color Stability During Retail Display Differs Among Muscles in Pork

The objectives of this study were to determine differences in color stability among pork muscles and whether changes in color measurements for longissimus dorsi (LD) were related to changes for triceps brachii (TB) or psoas major (PM). The LD, TB, and PM from 20 pigs were aged in vacuum packages for 21 d, then fabricated into 3 chops per muscle. All chops from a single muscle were overwrapped, displayed for 5 d under constant lighting, and evaluated daily for instrumental color, myoglobin forms, and subjective visual discoloration. Chops were removed on day 1, 3, or 5 to measure oxygen consumption (OC) and metmyoglobin reducing activity (MRA). Data were analyzed using the MIXED procedure of SAS as repeated measures. Pearson correlation coefficients were determined using the CORR procedure. Over the 5-d display period, TB and PM chops had greater changes in a*, b*, chroma, 630/580 nm ratio, deoxymyoglobin, and oxymyoglobin compared to LD chops (display time × muscle interaction P ≤ 0.01), but TB and PM did not differ from each other (P ≥ 0.07). Conversely, LD had decreased OC and increased MRA on each display day compared to TB and PM (P < 0.01). Using 20% discolored on day 5 of display as a threshold for acceptability, 85% of LD samples were considered acceptable whereas only 5% and 20% of TB and PM samples were considered accept-able, respectively. Changes in LD were correlated with TB and PM changes for redness (0.51 ≤ r ≤ 0.55; P ≤ 0.02), and they trended toward a correlation with changes in TB and PM 630/580 nm ratio and hue angle (0.39 ≤ r ≤ 0.63). Chops from TB and PM were less color stable during display, but LD changes were not consistently correlated with changes in other muscles.